Conventional infrared imaging devices often use arrays of infrared sensors to capture thermal images of scenes. The infrared sensors are typically implemented in rows and columns to provide generally square or rectangular arrays. Such arrays are usually positioned within imaging devices such that, when the imaging devices are positioned to capture an image of a scene, the rows of sensors are oriented substantially parallel to the ground, and the columns of sensors are oriented substantially perpendicular to the ground.
In many environments, various features of a scene may be disposed in substantially horizontal and/or substantially vertical directions (e.g., relative to the ground or another reference plane). This is true for many manmade structures such as buildings, streets, sidewalks, and other structures. Many naturally occurring features are similarly disposed such as trees, rivers, other bodies of water, and other features. As a result, the horizontal and vertical features of an imaged scene may generally align with the rows and columns of the sensor arrays of conventional infrared imaging devices.
Sensor arrays may exhibit various types of noise (e.g., fixed pattern noise (FPN) or others) that may be substantially correlated to rows and/or columns of infrared sensors. For example, some FPN that appears as column noise may be caused by variations in column amplifiers which may inhibit the ability to distinguish between desired vertical features of a scene and vertical FPN.
Existing techniques used to reduce row and column noise can lead to unsatisfactory results. For example, existing noise reduction techniques may leave artifacts (e.g., image distortion or residual noise) in rows and columns of pixels of captured images. Such row and column noise artifacts may be exacerbated when features of an imaged scene are substantially aligned with rows and columns of the imager as is the case with conventionally oriented sensor arrays.